In vertebrate animals, the heart is a hollow muscular organ having four pumping chambers: the left atrium, the left ventricle, the right atrium and the right ventricle. The atria are isolated from their respective ventricles by one-way valves located at the respective atrial-ventricular junctions. These valves are identified as the mitral (or bicuspid) valve on the left side of the heart, and tricuspid valve on the right side of the heart. The exit valves from the left and right ventricles are identified as the aortic and pulmonary valves, respectively.
The valves of the heart are positioned in valvular annuluses that comprise dense fibrous rings attached either directly or indirectly to the atrial and ventricular muscle fibers. Valve leaflets comprising flexible collagenous structures are attached to, and extend inwardly from, the annuluses to meet at coapting edges. The aortic, tricuspid and pulmonary valves each have three leaflets, while the mitral valve only has two. In normal operation, the leaflets of the mitral valve open as left ventricle dilates thereby permitting blood to flow from the left atrium into the left ventricle. The leaflets then coapt (i.e. close) during the contraction cycle of the left ventricle, thereby preventing the blood from returning to the left atrium and forcing the blood to exit the left ventricle through the aortic valve. Similarly, the tricuspid valve regulates flow from the right atrium into the right ventricle, and the pulmonary valve regulates blood exiting the right ventricle.
For a number of clinical reasons various problems with heart valves can develop. One common form of heart disease involves the deterioration or degradation of the heart valves, which leads to stenosis and/or insufficiency. Heart valve stenosis is a condition in which the valve does not open properly. Insufficiency is a condition in which the valve does not close properly. Insufficiency of the mitral valve, most common because of the relatively high fluid pressures in the left ventricle, results in mitral valve regurgitation (“MR”), a condition in which blood reverses its intended course and flows “backward” from the left ventricle to the left atrium during heart contractions.
A number of surgical techniques have been developed to repair degraded or otherwise incompetent heart valves. A common procedure involves replacement of a native aortic or mitral valve with a prosthetic heart valve. Such procedures require the surgeon to access the heart through the patient's chest (or possibly percutaneously), surgically remove the incompetent native heart valve and associated tissue, remodel the surrounding valve annulus, and secure a replacement valve in the remodeled annulus. While these procedures can be very effective, there are associated shortcomings. For example, the highly invasive nature of the implantation procedure typically results in substantial patient discomfort and requires patients to remain hospitalized for extended recovery periods. In addition, the two basic types of commercially available replacement valves, mechanical valves, and tissue valves, have shortcomings of their own. Mechanical replacement valves typically offer extended operational lifetimes, but the patient is usually required to maintain a regimen of anti-coagulant drugs for the remainder of his or her life. Tissue valves typically offer a higher degree of acceptance by the body thereby reducing or eliminating the need for anti-coagulants, but the operational lifetimes of tissue valves is typically shorter than mechanical valves and thus may require a subsequent replacement(s).
As an alternative to prosthetic heart valve replacement, it is often preferable to remodel the native heart valve and/or surrounding tissue. Remodeling procedures often preserve left ventricular function better than mitral valve replacement because the subvalvular papillary muscles and chordae tendineae are preserved (most prosthetic valves do not utilize these muscles). Typically, valvular remodeling is accomplished by implanting a prosthetic ring (“annuloplasty ring”) into the valve annulus to reduce and/or stabilize the structure of the annulus. Annuloplasty rings are typically constructed of a resilient core covered with a fabric sewing material. Annuloplasty procedures can be performed alone, or they can be performed in conjunction with other procedures such as leaflet repair. Although annuloplasty procedures have become popular and well accepted, reshaping the surrounding annulus and traditional leaflet repairs do not always lead to optimum leaflet coaptation. As a result, some patients may still experience residual mitral valve regurgitation following annuloplasty procedures.
A recently developed technique known as a “bow-tie” repair has also been advocated for repairing insufficient heart valves, in particular the mitral valve. The mitral valve bow-tie technique involves, in its simplest form, suturing the anterior and posterior leaflets together near the middle of their coapting edges, thereby causing blood to flow through two newly formed side openings. While this does reduce the volume of blood that flows from the atrium to the ventricle, this loss is more than compensated by improved leaflet coaptation, which reduces mitral regurgitation. As originally developed by Dr. Ottavio Alfieri, this process involved arresting the heart, and placing the patient on extra corporeal bypass and required invasive surgery to access and suture the leaflets together. More recently, however, some have advocated a “beating heart” procedure in which the leaflets are accessed remotely and the heart remains active throughout the procedure.
A particular method for performing a beating heart bow-tie procedure (i.e. without extra corporeal bypass) has been proposed by Dr. Mehmet Oz, of Columbia University. The method and devices for performing the method are described in PCT publication WO 99/00059, published Jan. 7, 1999. In one embodiment of the disclosed procedure, the associated device consists of a forceps-like grasper used to grasp and hold the mitral valve leaflets in a coapted position for suturing. Since the mitral valve leaflets meet and curve toward and slightly into the left ventricular cavity at their mating edges, the grasper device is passed through a sealed aperture in the apex of the left ventricle. The edges of the mating mitral valve leaflets are then grasped and held together, and a fastening device such as a clip or suture is utilized to fasten them. The fastening device should be applied to the leaflet tissue with sufficient tissue purchase to prevent tear out or other failure, but close enough to the edges to ensure that the newly created side holes are as large as possible. The Mehmet Oz disclosure thus illustrates that teeth of the grasper device can be linearly slidable with respect to one another so as to permit alignment of the mitral valve leaflets prior to fastening. Since the procedure is done on a beating heart, it will be readily understood that the pressures and motions within the left ventricle and mitral valve leaflets are severe. Thus the procedure taught by Dr. Mehmet Oz is very skill-intensive.
The bow-tie technique has proved to be a viable alternative for treating otherwise incompetent heart valves. Nonetheless, several shortcomings associated with current bow-tie procedures have been identified. Current systems include devices having mechanical graspers, barbed members, and vacuum devices that simultaneously capture and retain the valve leaflets prior to applying a fastening device thereto. Often, use of these devices results in the less than optimal leaflet stabilization and fastener placement. Many of these problems arise from the fact that the surgeon is required to capture, retain and fasten the leaflets in one relatively inflexible procedure. These difficulties are compounded when the leaflets are small or calcified making them difficult to pull together, and in beating heart procedures in which the leaflets are actively functioning throughout the surgery. In light of the foregoing, there is presently a need for improved systems for stabilizing multiple tissue heart valve leaflets and placing a fastening device there between. More specifically, there is a present need for an improved bow-tie procedure for repairing a patient's mitral valve.